MONDAY, Dec. 21, 2015 -- Gay and bisexual men who have abstained from sex for one year will now be allowed to donate blood in the United States.

The new policy, announced Monday by the U.S. Food and Drug Administration, reverses a three-decades-old ban on donations from this group of men that traces back to the start of the AIDS epidemic.

"The FDA's responsibility is to maintain a high level of blood product safety for people whose lives depend on it," FDA Acting Commissioner Stephen Ostroff said in an agency news release. "We have taken great care to ensure this policy revision is backed by sound science and continues to protect our blood supply."

The FDA said it was changing its policy based on data from other countries that show allowing such donations would not increase the risk of HIV-tainted blood entering America's blood supply.

FDA officials have estimated that about half of the people previously barred from donating blood would be able to donate under the new policy.

"We've taken great care to ensure that the revised policy continues to protect our blood supply," Dr. Peter Marks, deputy director of the FDA's Center for Biologics Evaluation and Research, said during a news conference Monday.

The new recommendation includes "a 12-month deferral period for the most recent sexual contact for men who have sex with men, rather than the existing indefinite deferral," Marks added.

"As we recommend these changes, we are reaffirming a commitment to further progressing blood donor deferral policies as new scientific information becomes available," Marks said.

The change will also better align the FDA's donation policy for gay and bisexual men with its policies regarding other people potentially exposed to HIV, the virus that causes AIDS, officials said.

For example, there's currently a maximum one-year deferral policy in the United States for blood donations by men who have had sex with an HIV-positive woman or commercial sex workers. The same goes for women who have had sex with HIV-positive men.

However, sexually active gay men in a monogamous relationship would not be allowed to donate blood under the new policy.

The FDA said it will also implement a national blood surveillance system that will help the agency monitor the effect of the policy change and ensure the safety of the blood supply, health officials said.

The American Red Cross has found that the risk of an HIV-tainted blood donation getting into the national blood supply is about 1 in every 1.5 million units, agency officials said.

The FDA adopted a permanent ban on blood donations from men who have sex with men at the dawn of the AIDS crisis. Proponents of lifting the ban have said changing times and technological advances have rendered the decades-old policy obsolete. The FDA first proposed lifting the ban last December.

Other countries have already moved to limit their bans on blood donations from gay men in recent years. Canada has changed its policy to a five-year deferral policy (meaning blood donation is allowed if the man has not had sexual contact for five years); the United Kingdom and Australia have a one-year deferral policy; and South Africa has a six-month deferral policy.